Nick Clegg has said the Liberal Democrats would block any further plans to bomb ISIS, potentially shattering coalition unity on the subject. He warned that although his party supported attacks in Iraq against ISIS they would oppose any efforts to expand the mission to include targets in Syria.

The Deputy Prime Minister suggested he would prevent David Cameron from holding a second vote on any attack on targets in Syria. Clegg’s party did support the government in the vote last month to when attacking ISIS in Iraq at request of the government in Baghdad. The vote was passed by 524 to 43, with the support of all the major parties.

Clegg told the BBC’s Andrew Marr show: “I wouldn’t advocate that we extend the air campaign into Syria. That’s why we didn’t do it last week.” When he was asked whether he would support allowing a vote on the bombing of Syria he said: “No, well it won’t come to a vote unless the Government proposes it, and what I’m saying is the Government is not proposing it right now.

“We need to persuade the British people, indeed Parliament as well, that every time we put servicemen and servicewomen in harm’s way, we do so with a clear strategy in mind. And I think the combination of air strikes and ground forces needs to be properly thought through. That was obvious in Iraq. It’s a little bit more complicated in Syria.”

The news came as Idris Hassan, a spokesman for Kurdish fighters in Syria warned that the current strategy in Syria was not working. He told the Guardian: “Air strikes alone are really not enough to defeat Isis in Kobani (Syria)… They are besieging the city on three sides, and fighter jets simply cannot hit each and every Isis fighter on the ground.”

Conservatives expressed alarm that the Liberal Democrats would not support an expanded mission. The Mail on Sunday reported a senior Conservative source saying: “Clegg seems to have shifted. The question is whether it is just a shift to get him through his party conference, or something more serious.” Former Tory defence minister Sir Gerald Howarth went even further accusing Clegg of being “utterly irresponsible”.

The party is worried the Liberal Democrats would block further military action against ISIS in order to avoid electoral meltdown in May’s general election. Clegg and his party have seen a remarkable fall in the polls from 23 percent in 2010 to just 7 percent in the latest polls.

They will hope their annual conference in Glasgow will give them a bounce before next years election.